Prosthetic elements are known, which are applied in many parts of the human body, such as for example the knees, shoulders or femoral extremities.
A prosthetic element is known, for example from EP-A-2164428 in the name of the present Applicant, with a cellular structure usable as an acetabulum cup for a femoral prosthesis in implant operations in the acetabulum of the pelvis. The prosthetic element, in this case, has the function of housing a prosthetic head, or an insert, for the acetabulum cup, into which in turn a femoral prosthesis is inserted. The prosthetic element comprises a cap of metal material, the body of which comprises a three-dimensional lattice, trabecular shaped, with a predefined and desired thickness. The lattice is formed by a plurality of open and communicating cavities, which are connected both toward the inside and toward the outside of the cap.
A prosthetic element is also known from WO 2011/138646, also in the name of the present Applicant, which can be used for bone implant operations, such as for example femoral, shoulder or knee prostheses. The prosthetic element in this case comprises a metal support and an insert made of plastic material. The metal support in its turn comprises a first surface, to which said plastic insert is coupled, and a second surface to which the bone part on which the prosthesis is fitted is intended to be coupled. The first surface comprises cavities or holes, suitable to anchor and make solid the plastic material which forms the insert, while the second surface comprises a porous layer of a trabecular shape suitable to optimize the anchoring of the bone. The cited first and second surface are separated by a compact layer, having the function of stopping the plastic material in the injection step for the formation of the plastic insert.
However, in many cases prostheses are required to be applied in bone parts that have very much smaller sizes compared to those cited above, such as for example in the reconstruction of small joints, like those of a hand or a foot, or in the case of dental implants.
The solutions cited above are not suitable for such applications, for example because of the inadequate size of the pores of the porous layer of a trabecular shape.
Some solutions in the state of the art have tackled these problems.
For example, from document EP 1.438.937 a transcutaneous prosthetic element is known, used to recover the functions of partially amputated fingers. The prosthetic element consists of an extracorporeal part, able to substitute the missing end of a finger, and an intracorporeal part consisting of a hollow tubular rod, preferably made of bio-compatible material. The tubular rod is externally lined, for a portion thereof, by a porous layer with three-dimensional meshes, of a not precisely defined shape, for bone integration.
An apparatus for the reconstruction of a metatarsus-phalanx joint is also known from WO 2006/099886.
This apparatus, preferably made of bio-compatible metal, is formed by a part shaped like a concave capsule facing toward the joint, once the apparatus is implanted, and by a rod which instead is inserted in the phalanges. A portion of surface conformed as a net with an open three-dimensional mesh is provided on the rod and inside the concave part.
One disadvantage of these embodiments is that the porous structures of the surfaces for the bone integration, because of the geometry of the meshes, entail a difficult and uneven bone integration.
Another disadvantage of these embodiments is that the shape of the part of the prosthetic element to be inserted into the bony extremity is not optimal for anchorage.
Another disadvantage is the lack of structural continuity between internal rod and external trabecular part.
An intraosseous implant is also known from DE 202004013500U1, for the reconstruction of a tooth, suitable for insertion in the jaw bone, equipped with a covering structure obtained by sintering titanium balls on the external surface of a support rod
From the article by Collins, M et al, “Zimmer Trabecular Metal Dental Implant Research: A Brief Overview”, a dental implant is also known, having an external layer of trabecular metal in tantalum which covers a structure of titanium alloy. The trabecular metal is formed by applying the tantalum on a substrate of vitreous carbon through a chemical process of deposition through steam.
One disadvantage of these embodiments is that the porous structure is integrated only in a step after the formation of the other structures of the prosthetic elements, and therefore do not allow to overcome limitations of a structural type deriving from the physical and mechanical discontinuity between the different parts which make up the prosthetic element.
Moreover, the production processes needed to make these elements are rather complex, require a long time, are difficult to standardize and produce results that are often dissimilar and not always effective.
One purpose of the present invention is therefore to obtain a prosthetic element with a trabecular structure intended for bone integration in the case of reconstruction of small joints, such as for example those of a hand or foot, and for dental implants, which has higher structural and mechanical characteristics and a higher capacity of bone integration.
Another purpose is to perfect a method to make said prosthetic element, suitable to be used in the reconstruction of small joints and dental implants.
It is another purpose of the present invention to obtain both a trabecular structure with an external conformation which allows the best adhesion and integration possible of the bone, and also an overall shape which guarantees an efficient anchorage, of both the extremities and the central body, to the bone and tissue structures of the patient.
It is also a purpose of the present invention to make a prosthetic element which has a trabecular structure with improved mechanical properties, which allows a uniform bone integration and can be obtained with a highly standardized and repeatable process with great efficiency and conformity of the results.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.